"His United Future Party gained just 13,443 votes nationwide at the 2011 election," Cosgrove said.

"To put that in perspective, he gained only 1705 more votes than the Aotearoa Legalise Cannabis Party. Imagine the outcry if that party was in a position to decide such a critical issue as the very future of assets we have built up and proudly own.''

Dunne had "campaigned on the asset sales issue using language designed to confuse voters''.

In a statement, Dunne said he had intended to speak in the debate today, but was unable to attend because of a family funeral.

The legislation was "an innovative way to raise much-needed capital'' for State Owned Enterprises to grow.

Without the partial sales, the country would have to borrow more to fund the companies, allow companies to raise their charges, or raise taxes.

"We say none of those options are on. The self-righteous opponents of this bill need to say which ones they will inflict on New Zealand's taxpayers,'' Dunne said.

"This legislation is an innovative way to raise much-needed capital and at the same time gives New Zealanders a chance to invest in their own futures."

His vote for the bill was cast by proxy by National - which prompted cries of "shame'' from the opposition benches.

The sale of Mighty River Power is expected to net $1.7b to $1.8b. Prime Minister John Key yesterday said the two other power companies - Meridian and Genesis - would follow though it had not been decided in what order. The sell down of those two would add another $3.96b to $4.23b revenue from the programme.

Key said there was "not necessarily a high level of understanding" about the sales programme among the public.

"I think New Zealanders will get a better understanding of this when they actually see the companies brought to market and when they see that the day after the mixed ownership model float, in fact, the sun will come up and the company will look very much like Air New Zealand," Key said.